Self-Assembly Design of a Robust 2D Frustrated Magnet with Bilayer Tetragonal Spin-Lattice.

Xing, Jianpei; Zhao, Bo; Kang, Jinchao; Qi, Yan; Liu, Qinxi; Jiang, Xue; Zhao, Jijun · Nano Lett · 2025

basic_science · Level V

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Abstract

We intentionally designed a stable two-dimensional (2D) bilayer dimer system, OsFeP<sub>4</sub>, which serves as a tunable spin-5/2 <i>J</i><sub>1</sub>-<i>J</i><sub>2</sub> anisotropic Heisenberg-like model to investigate frustrated magnetism. The frustrated state of 2D OsFeP<sub>4</sub> originates from the robust intradimer ferromagnetic (FM) exchange coupling (<i>J</i><sub>⊥</sub>) and a subtle competition between P<sub>4</sub> molecules mediating interdimer ferromagnetic (<i>J</i><sub>∥</sub>) and antiferromagnetic (AFM) exchange coupling (<i>J</i><sub>×</sub>). This is further supported by a significant broadening of the specific heat peak, a high frustration factor (θ<sub>CW</sub>/<i>T</i><sub>N</sub>) of 4.17, the peak at the gamma point in the static structural factor, and short-range spin textures. Moreover, we employ strain to modulate the frustration parameter <i>J</i><sub>×</sub>/<i>J</i><sub>∥</sub> from 0.23 to 0.4 and spin direction from in-plane to out-of-plane. The FM, AFM, and frustrated phase transitions are identified in the <i>J</i><sub>⊥</sub>-<i>J</i><sub>×</sub>-<i>J</i><sub>∥</sub> ternary phase diagram. This work will enrich our understanding of the frustration mechanisms in the 2D limit.